Small-screen computing devices continue to proliferate, such as smartphones, computing bracelets, rings, and watches. Like many computing devices, these small-screen devices often use virtual keyboards to interact with users. On these small screens, however, many people find interacting through virtual keyboards to be difficult, as they often result in slow and inaccurate inputs. This frustrates users and limits the applicability of small-screen computing devices.
To address this problem, optical finger- and hand-tracking techniques have been developed, which enable gesture tracking not made on the screen. These optical techniques, however, have been large, costly, or inaccurate thereby limiting their usefulness in addressing usability issues with small-screen computing devices. Other conventional techniques have also been attempted with little success, including radar-tracking systems. These radar tracking systems struggle to determine small gesture motions without having large, complex, or expensive radar systems due to the resolution of the radar tracking system being constrained by the hardware of the radar system.